Correction for the bone-induced beam hardening to X-ray CT images has usually been made as found in Joseph, et al. literatures (Joseph, et al. A Method for Correcting Bone Induced Artifacts in Computed Tomography Scanners, Journal of Computer Assisted Tomography vol. 2, p 100-108, Jan. 1978) by scanning the reconstructed image elements, calculating the correction amount from the pass length of the soft tissue portion and bone (separated with CT values) contained therein, correcting the same with the actual scan data and, thereafter, reconstructing them again.
However, the method has the following problems.
(1) Since twice reconstructing and once scanning of the image elements are required, the computing amount is enormous and no high speed processing can be expected
(2) While it is customary to erase the actual scan data after once reconstructing the image to prepare for the next scanning, the actual scan data have to be preserved after the image reconstruction till the correction of the actual scan data and the second image reconstruction have been completed.